Multiple rheostat and potentiometer



P 1946. R.' J. MILLER 2,398,758

MULTIPLE RHEOSTAT AND POTENTIOMETER Filed March '7, 1944,

I //6 0 fi +{7 Y ms INVENTOR 4 finr/vo/vp J/V/LLEG Patented Apr. 16, 1946 MULTIPLE RHEOSTAT AND POTENTIOMETER Raymond J. Miller, Detroit, Mich.

Application March 7, 1944, Serial No. 525,384

12 Claims.

This invention relates to electrical resistance varying devices, and more particularly to multiple rheostats and potentiometers.

Rheostats and potentiometers are widely used in industry to vary the current supplied to all types of electrically actuated devices, and to transmit a controlled proportion of current from a single source to a plurality of electrically actuated devices. I

In rheostats and potentiometers of the types heretofore employed, a separate electrical resistance element has been provided for each contact-or member, and where multiple controls were required it was customary to employ the necessary number of separate and independent units each having a separate resistance element.

I have found that a plurality of contactor members may be employed with a single resistance element to, in effect provide a plurality of rheostats or potentiometers all operating on a single resistance element. More compact applications incorporating variable resistors can therefore be designed with these new multiple rheostats and potentiometers to facilitate centralized positive control of electrical units and provide improved operating efficiency and accessibility with a substantial saving in weight and space requirements.

An object of this invention is therefore to provide amultiple rheostat or potentiometer having a plurality of contactors adapted to engage a single electrical resistance element.

A further Object of the invention is to provide an electrical resistance varying device wherein a plurality of spaced contactors insulated from each other engage a single resistance element to provide a multiple rheostat or potentiometer.

Another object resides in the provision of a rheostat having a plurality of separately actuated control members insulated from each other, and engaging a single resistance element whereby a plurality of variable current intensities can be obtained from a single resistance element.

Yet a further objectis to provide a multiple potentiometer having a plurality of spaced contactors engaging a single resistance element, operable with a relay switch so that the opposite ends of the resistance element from the point of engagement of a contactor member may function separately, or opposite ends of the resistance element from the points of contact of spaced contactors may be separately employed.

Still another object of the invention is to provide a potentiometer wherein a single resistance element is engaged by aplurality of spaced manually operable contactors or resistance varying members adapted to be so connected that a large number of circuits can be made in'combination with one another, such for example as one circuit to include the resistance of the resistance element from the point of contact of one of the conmotors to one end of the resistance element. an-

other circuit to include the resistance of the resistance element from the point of contact of another of the contactors to either end of the resistance elements, and a third circuit to include the resistance of the resistance element between the points of contact of the aforementioned contactors.

A further object is to provide a multiple resistance varying device having a plurality of spaced separately actuated contactor members grouped around a single electrical resistance element whereby the space and weight requirements for an equivalent number of resistance varying devices is materially reduced.

Yet a still further object of the invention resides in the provision ofa multiple resistance varying member having a plurality of contactors shaped for example in the form of twisted straps fioatingly mounted on a single resistance member, and wherein each contactor is insulated from the other contactors to successively engage spaced .convolutions of the resistance member to permit accurate variation of the electric current supplied by each contactor member without influencing the current delivered by any of the other contactor members.

Still another object of the invention is to provide a rheostat or potentiometer having electrical connections to permit switching over to employ opposite ends of the resistance element as a contactor passes over the point of balanced electrical resistance of the resistance element.

Another object is to provide an improved mounting and electrical connection whereby a resistance varying contactor may be secured to an electrical resistance element.

. Other objects and advantages of this invention will be apparent from the following detailed description considered in connection with the accompanying drawings, submitted for purposes of illustration only and not intended to define the scope of the invention, reference being had for that purpose to the subjoined claims.

In the drawing wherein similar reference characters refer to similar parts throughout the several views.

Fig. 1 is a perspective view of a multiple rheostat embodying the invention.

Fig. 2 is a side elevation, partly in section, of l the device illustrated in Fig. 1.

Fig. 3 is an end elevation, partly in section, taken substantially on the line 3-3 of Fig. 2 looking in the'direction of the arrows.

Fig. 4 is an end elevation, taken substantially on the line 44 of Fig. 2, looking in the direction. of the arrows.

Fig. 5 is an enlarged fragmentary sectional viewshowing a modified form of mounting for securing a contactor member on the resistance element.

Fig. 6 is a longitudinal sectional view of a multiple potentiometer embodying the invention.

Fig. 7 is a fragmentary sectional view taken substantially on the line 'I--1 of Fig. 6 looking in the direction of the arrows.

Before explaining in detail the present invention it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawing, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Figs. 1 to 5 illustrate the invention as applied to rheostats wherein it is desired to vary the intensity of the electric current supplied to any electrically actuated device.

A single electric resistance element l may be formed of a resistance wire l2 wrapped about an insulating core l4 having front and back end plates l6 and 18. The resistance wire l2 may be of any suitable type, such for example as an insulated wire having an oxide or other coating thereon to permit wrapping the wire in such a manner that successive convolutions contact each other, or may be uninsulated and wrapped about the core M in such a manner that successive convolutions are spaced from each other. The core 14 and end plates l6 and I8 may be formed of any suitable insulating material such for example as Bakelite or tenite.

The front end plate I6 is provided with a radially extended flange 20 adapted to engage a panel or plate 22. A casing 24 concentrically mounted on the forward end of the resistance element 10 isprovlded to engage the panel 22 to be secured to the front end'plate i6 by means of spaced screws 26 to secure the unit in the panel 22.

A plurality of resistance varying contactor members carried by shafts 28, 30, 32, 34, 36 and 38 are mounted on the front and back end plates l and I8 and have actuating portions in the form of twisted straps or ribbons 40 to engage the resistance wire l2. Where an insulated wire I2 is employed, the insulating coating should be removed on the outer periphery of spaced convolutions to permit the edges of the contactor members to make electrical contact with successive convolutions of the resistance wire.

The front ends of the shafts 28, 30, 32, 34, 36 and 38 are provided with manually operable knobs 42, 44. 46, 48, 50 and 52 journalled in the front plate 16. Yielding means are provided to urge the contoured portions 40 of each of the contactor members into engagement with the resistance coil !2 to permit each contactor to maintain contact with the resistance element at a single point only. The yielding means associated with each contactor should be insulated from the yielding means associated with each of the other contactors, and separate yielding means may be associated with the front and back plates l6 and I8.

The front end of each of the shafts carrying the contactor members 40 may be yieldingly urged radially inwardly by a separate spring 54 havin a contoured portion 56 to lie in a groove 58 of its associated knob. Each of the springs 54 has extended portions 60 adapted to lie within a circumferentially extending groove 51 formed in the front plate IS.

The back ends of the shafts may be positioned in outwardly opening grooves or slots 62 formed in the back plate [8, and each shaft may be yieldingly urged radially inwardly by a separate spring 64 secured to the back plate 16 by means of a screw 66 as illustrated in Figs. 1, 2 and 4.

If desired each of the springs 64 may be secured to the back plate i8 by means of a bushing 68 pressed into the back plate l8 as illustrated in Fig. 5. The screw 66 may be threaded into the bushing 68 to secure the terminal 10 in place and to form an electrical connection with its associated contactor member through an associated spring 64 engaging the back ends of each of the shafts 28, 30, 32, 34, 36 and 38.

It will be noted that each of the resistance varying contactor members is floatingly mounted on the resistance element l0 and is insulated from each of the other contactor members. The actuating portion of each contactor member i twisted somewhat less than 180 degrees, and the knobs 42, 44, 46, 48, and 52 rotate through somewhat less degrees to prevent the contacting portions 40 from engaging the resistance wire 12 at more than a single point when operated from one extreme position to the other.

It will be understood that any type of contactor and actuating mechanism may be employed so long as each contactor is insulated from each other contactor, and does not simultaneously engage the resistance wire 12 at spaced points.

One end 12 of the resistance wire i2 is con nected to a terminal I4 preferably positioned in the back plate 18, and the other end 16 need not be connected to anything but may be projected through the core 14 and bent over to prevent the resistance coil from unwinding.

The operation of this embodiment of the invention is as follows. A source of electrical current supply i connected to the terminal 14 having the end 12 of the resistance wire 12 connected thereto. The current from the source flows through the resistance coil i2 decreasing in intensity as it travels through the wire toward the right hand end of the unit a viewed in Fig. 2. A plurality of diiferent electrically actuated devices may be connected to the terminals 10 operably connected through their associated contactor members 28, 30, 32, 34, 36 and 38. Electric current of any desired intensit may be obtained at each of the spaced terminals 10 by rotating the associated control knobs 42, 44, 46, 48. 50 and 52 to var the position of the contacting portion 40 of the associated contactor member.

When current of high intensity is desired at one of the outlets or terminals 10, the knob controlling the associated contactor may be rotated to cause the contacting portion of the bar 40 to engage the resistance wire I2 adjacent the left hand end of the resistance coil as viewed in Figs. 1 and 2. If current of lower intensity is required, the associated control knob may be rotated to shift the point of engagement of the contactor member with the resistance wire I 2 toward the right as viewed in Figs. 1 and 2 to increase the amount of resistance wire I2 through which the current must flow and therefore reduce the current intensity. When the contactor is positioned to engage the right hand end of the resistance wire l2, the entire resistance of the resistance coil i2 is in the circuit and current of minimum intensity will be supplied.

In view of the fact that each contactor member is insulated from each other contactor member, the position of one contactor and hence the current transmitted through the associated terminal has no effect on the position or operating characteristics of any of the other contactors members. For example one of the contactors may be positioned in engagement with the resistance coil adjacent the left hand end to transmit current of high intensity, another contactor member may be positioned to engage the right hand end of the coil I2 to transmit current of low intensity and the other contactor members may be so positioned as to transmit current of any desired extreme or intermediate intensity without in any way substantially influencing the current transmitted b any of the other contactor members.

It will be apparent that in these rheostats, current of a given intensity may be introduced through the terminal 14 and current of substantially any desired intensit within the limits of the design may be taken off simultaneously at a plurality of spaced points at any or all of the terminals 10. I

The embodiment of the invention illustrated in Figs. 6 and '7 is similar in many respects to that illustrated in Figs. lto 5. Corresponding parts have therefore been given corresponding reference numerals with the addition of 100.

It will be noted that the right hand end I16 of the resistance wire H2 is connected through a length of wire I18 to a terminal I80 positioned in the back plate II 8 to complete the circuit through the resistance coil H2 to operate the dcvice as a potentiometer.

The front end of each of the contactor memhers is connected to the resistance coil II2 by means of a spring I8I secured in the core H or in the front plate I I5, and having a hooked portion to engage its associated shaft to yieldingly urge the edge of the contact making portion I40 of the associated contactor member into engagement with the resistance wire H2. Each of the springs I8I is connected through a separate wire such as the wir I82 with a terminal I83 positioned in the back plate H8 to complete the circuit from the contacting portion of the contactor to the right hand end of the resistance coil I I2 as viewed in Fig. 6.

As illustrated each of the wires from each of the springs urging the front end of each of the contactor members into engagement with the resistance coil may extend through the center of the core I II) to its associated terminal I83 positioned in the back plate I I8. To avoid confusion only a single terminal I83 has been shown on the drawing. It will be noted that each of the control knobs is secured to its associated shaft by means of a stud I85 rather than by a press-fit as in the embodiment illustrated in Figs. 1 to 5.

The operation of this embodiment of the invention is as follows. A source of electric current may be connected with the terminal I14 to induce a current flow through the resistance wire I I2. Each of the contactors being insulated from all of the other contactors is operable independently of the other contactors to divide the current flow through the resistance wire and function as an independent potentiometer. Each of the contactor members may be set to transmit current of substantially any desired intensity through its associated terminals I10 and I8I positioned at opposite ends of the device by varying the distance of the point of engagement of the contactor member from the left hand end of the resistance coil H2.

Any desired circuit combination can be made employing either of the terminals I14 or I80 connected to opposite ends of the resistance element H2, and either of the terminals I10 or I83 connected to opposite ends of each of the contactor members I40. It will also be apparent that both 01' the terminals I14 and I80 connected to opposite ends of the resistance element I I2, and both of the terminals I 10 and I83 connected to opposite ends of each of the contactor members may also be connected to form a switch-over circuit to transmit current of maximum intensity when the contactor is in engagement with either end of the resistance coil and to transmit progressively decreasing current as the point of engagement of the contactor moves toward the center of the resistance element. When the point of balanced electrical resistance of the resistance element is passed over by progressive movement of the point of engagement of the contactor relative to the resistance element. the circuit automatically switches over to transmit to the terminals I 10 and I83 the resistance interposed by the portion of the resistance element having the least resistance.

A relay switch can be employed if desired, and opposite ends of the resistance element from the point of engagement of the contactor members with the resistance element can function separately, or opposite ends of the resistance coil from spaced contactor members can be employed.

It will also be apparent that any desired number of circuits can be made in combination with one another. For example one circuit can be connected to include the resistance from the point of engagement of the contactor member to one end of the resistance element, another circuit can be employed to include the resistance of the resistance element from the point of engagement of another of the contactor members to the same or the opposite end of the resistance element, and another circuit can be employed to include the resistance between the points of engagement of these two spaced contactor members.

Attention is called to the fact that the potentiometer illustrated in Figs, 6 and 7 may be operated as a rheostat by merely connecting the outlet to either of the terminals I10 or I83 of each of the contactor members with the device to be operated. In the embodiment of Figs. 1 to 5 the terminals 10 may if desired be connected to the right hand end of the contactor members as illustrated by the connection to the terminals I83 of Fig. 6. Also it will be apparent that the ter minal I connected to the right hand end of the resistance element II2 can be employed rather than the terminal I14 when the device of Fig. 6 is operated as a rheostat to employ the resistance of the resistance element from the right hand end.

Any desired number of contactors may be positioned about a single resistance element, the only limitation being that the contactors be insulated from each other and progressively movable over the resistance element. It will be apparent that any desired motion transmitting means ma be employed to actuate the contactor members. Levers may be employed in lieu of the control knobs illustrated, and where it is desired to position a large number of contactor members about a single resistance element, levers and knobs may be alternately spaced, or radially movable levers alone may be employed.

I claim:

1. A multiple electrical resistance varying device comprising a single insulating core, a resistance element wrapped about the core, insulating end plates on the core, a plurality of spaced contactor members mounted on the end plates and each having a body portion in the form of a twisted strap to engage successive convolutions of the-resistance element as the contactor member is oscillated, yielding means urging the body portions of the contactor members into engagement with the resistance element, manually operable means to selectively actuate each of the contactor members, and an electrical outlet terminal associated with each of the contactor members.

2. A rheostat comprising a single resistance element, a plurality of spaced contactor members in the form of twisted straps insulated from each other and movably mounted on the resistance element to vary the point of engagement with the resistance element, manually operable means to actuate each contactor member, means to energize the resistance element, and an electrical outlet terminal associated with each contactor mem her.

3. A rheostat comprising a single insulating core, a resistance element wrapped about the core, insulating end plates on the core, a plurality of spaced contactor members mounted on the end plates and having body portions in the form of twisted straps to engage successive convolutions of the resistance element as the contactor members are oscillated," yielding means urging the edges of the body portions of the contactor members into engagement with resistance element, and manually operable means to selectively actuate each of the contactor members.

4. A multiple rheostat comprising a wound electrical resistance coil, means to connect one end of the coil to an electric current, a plurality of spaced contactor members in the form of twisted straps insulated from each other and mounted for edge engagement with the resistance coil, means to move each contactor member to shift its point of engagement with the resistance coil, and electric current outlet means associated with each contactor member.

5. A rheostat comprising an insulated core having spaced insulated end plates, an electrical resistance element wrapped about the core, means to energize the resistance element, a plurality of spaced contactor members in the form of twisted straps carried by the end plates and movable to engage successively spaced convolutions of the resistance element, each contactor member being insulated from each other contactor member, manually operable means to move each contactor member separately, and electric outlet means associated with each contactor member.

6. A multiple rheostat comprising a cylindrical resistance element having an insulated core and end members, a resistance element wrapped about the core, a plurality of contactor members in the form of twisted straps journalled for oscillation on the end members, a spring secured in one of the end members to yieldingly urge the contactor into edge engagement with the resistance element, each contactor member being insulated from each other contactor member, separate manually operable means to actuate each of the contactor members to engage successive convolutions of the resistance element, and electric outlet means associated with each contactor member.

7. A potentiometer comprising a cylindrical insulating core, a resistance element wrapped about the core, insulating end plates on the core, a plurality of spaced contactor members mounted on the end plates and having body portions in the form of twisted straps to engage successive convolutions of the resistance element as the contactor members are oscillated, yielding means urging the body portions of the contactor members into engagement with the resistance element,

manually operable means to selectively actuate each of the contactor members, and electric current outlet means associated with opposite ends of each of the contactor members.

8. In a multiple potentiometer a cylindrical resistance element having insulated core and end plates, a resistance element wrapped about the core, a plurality of contactors having spaced shaft portions journalled for oscillation on the end plates and body portions in the form of twisted straps to successively engage spaced convolutions of the resistance element when the contactors are oscillated, each contactor being insulated from each other contactor, yielding means urging the body portions of the contactors into engagement with the resistance element, electrical outlet means associated with spaced portions of each contactor, and manually operable means to oscillate each contactor.

9. An electrical device comprising a resistance element in cylindrical form, a plurality of contactor members in the form of twisted straps disposed peripherally about the resistance element and having edge contact therewith, each of said contactor members being rotatable on its own axis to shift its point of contact longitudinally of the resistance element, means for supplying electrical potential to one end of the resistance element, and separate electrical connections for each of the contactor members.

10. An electrical device comprising a resistance element in cylindrical form, a plurality of contactor members in the form of twisted straps disposed peripherally about the resistance element in parallelism therewith and having edge contact therewith, each of said contactor members being rotatable on its own axis to shift its point of contact longitudinally of the resistance element, yielding means at both ends of each resistance element to maintain the same in contact with the resistance element, connecting means for supplying electrical potential to one end of the resistance element, and separate electrical connections for each of the contactor members.

11. An electrical device comprising a resistance element in helical form, a contactor member in the form of a twisted strap having a helical edge, said contactor member being mounted at the periphery of the resistance element in parallelism therewith and having a helical edge in contact at one point with the resistance element, means for rotating the contactor member to shift the point of contact longitudinally of the resistance element, yielding means for urging the edge of the contactor member into contact with the resistance element, a connection for supplying electrical potential at one end of the resistance element, and a second connection leading from one end of said contactor member.

12. An electrical device comprising a resistance element in helical form, a contactor member rotatably mounted adjacent the resistance element and in parallelism therewith, said contactor member being in the form of a metallic ribbon twisted through less than and having edge contact with the resistance element at one point only, yielding means urging the contactor member into contact with the resistance element, means for rotating the contactor member on its own axis to shift its point of contact longitudinally of the resistance element, and electrical connecting means to said resistance element and said contactor member,

RAYIVIOND J. MILLER. 

